Hydraulic pumping unit



Oct. 23, 1951 P. E. Nou. ET A1. 2,572,748

HYDRAULIC PUMPING UNIT J8 f M 102 l 94 ToAccuMuLAron. g

f3 ro Risenvom I FROM CYLINDER.

LINE C2 INVENTORS 276 0m/L Nou.

man cnmnea MNE Ca mom Pump By ZW///- ,qu-Q

Ma/4x9 Oct. 23, 1951 P. E. NOLL ET AL HYDRAULIC PUMPING UNIT 5Sheets-Sheet 2 Filed NOV. 6, 1948 Oct. 23, 1951 P. E. NoLl. ET AL2,572,748

HYDRAULIC PUMPING UNIT Filed Nov. 6, 1948 3 Sheets-Sheet 3 t JM JeffLowfa UPR. No oF .5 3.5 f" j Acca .-DECEL.

Patented Oct. 23, 1951 UNITED STATES PATENT QFFlj-)CE 2,572,748HYDRAULIC PUMPING'UNIT Application November 6, 1948, Serial No. 58,714aolaimsl (C1. 6'0"-5'2) Our invention relates. to.` hydraulic pumpingunits, and has particular reference to.. a. precise control circuit forcontrolling the actuation-of. a ram. in a hydraulic cylinder, which`ram' may be usedr for exampleY to actuate a reciprocating mechanicalpump'- disposedy in` an oil well;

The principal componentsl of our hydraulic system are similar tov thosedisclosed' in patent application Serial No. 668,942, iiled May*10; 1946,in the .names ofA Paul E. Noll, CharlesW. Crawford, T; DwightAller, andAlbert R. Retheyf,` and Which. issued as Patent No. 2504218, April 18,1950. In general, a prime mover drives a pump which takes hydraulicfluidfrom a reservoirr and delivers it under pressure to' afour-wayfvalve. The valve alternately connects opposite ends ofahydraulic cylinder to the'v pressure ui'dfand to exhaust,y to cause thepiston in the'cylinder tofbe reciprocated. The ram connected to thepiston may be coupled directly or indirectly to a pump, and for oil wellpumping may be coupled to the upper end of ar string of' sucker rods,the lower end of which may be connected to a pumpl dis' posedv deepWithin an oil well. Anaccumulator' is customarily provided to assist onthe pumping stroke of the unit and thereby reduce: the-*maximum pressurerequired from the pump and in addition substantiallyv equalize thepressurerequired from the pump on the pumping stroke and the returnstroke of the ram; that is, on the re` turn stroke the pressure of theaccumulator opposes the pump pressure.

Our invention includes a novel circuit for controlling the reversal ofAthe hydraulicl ram:v at the ends of each stroke. Due tothe inertiaI oftlie sucker rod string and? thecolumn of'- oil being lifted, stresses ofserious consequence may-be iinposed on the rods lay-rapid reversalsfatth-eends of 'eachstroke.v It is highlydesirable; therefore, that theArods be'deceleratedI andA accelerated very gradually, particularlyv atthe lower reversal. This gradual deceleration and acceleration may beaccomplished in accordance with lour invention by by-passing pressurefluid'v at the extremes of travel of the ram so that the volume oftheuid passing throughthe four-way control valve is reduced, thus graduallyslowingA` the ram toa stop.

In order to permit close spacing of the subsurface oil pump, thusreducingA its clearance and y ployed to establish the reversalpoint,"but instead l thei piston is :hydraulically suspended throughoutthe reversal'. Since the counterbalance pressure tends to assist indecelerating the ramat the bot;- tom reversal, variation in, thatpressure might cause variation in the reversal point. We regulate,lprecisely the lower end point or travel of, the piSllOILby maintainingthe counterbalance pres,- sure within close limits by building up or:relieving gas pressure according to Whether there is over-travel orunder-travel of the piston; With re,- spect to.- ai preselected bottomvreversalv point. 'thus the, counterbalance pressure is utilized; asv acontrol-Vmedium for end. reversal point, and our invention providesapparatus: for continuously .ande automatically controlling this;pressure;V

It isrtherefore an object of our invention 'to providergradualaccelerationand deceleration of the rram in. a hydraulic actuating.cylinder by shunting or lov-passing pressure fluid Another object of ourinventionr is to. provide a; hydraulicy pumping unitxincorporating a.bypa'ss. action and a four-way valveenergizedat the same time by meansof a single mechanical. elementassociatedf with thestroke of theactuating ram. y

A furtherv object ofour invention is, to. provide a hydraulic actuatingunit with a by-passvalve anda four-way valve wherein a time delay deviceis coupledwith the four-.Way valve to permit synchronized actuationv ofthe by-passvalve andthe four-:way valve to effect deceleration,reversal, and'V acceleration.

A further object of our inventionistopfprovide a hydraulic pumping unitincorporating a counterbalancing device of the compressedigas type,withV means for automatically. maintaining the gas r pressure.

Still-another object oifour invention issto pr'olvide a hydraulicactuating -un-it inlwhioh the pistonis hydraulicallysuspended throughoutits reversals and in whichmeans are provided to. prevent variation inthe lower reversal` peint.l

Another object ofV our invention is to provide-a hydraulic pumping unitin which variation of the lower reversal pointV is` prevented byautomatically increasing or reducing the counterbalancepressurefaccording to Whether the pistonj tends to over-travel orunder-travel a preselected reversal point.

It is also'a feature of our invention to provide anautomatic'loW-coritrol valve in the counterbalance circuit to preventdarn-age toftheunit incase of breakage-,oi the rod string;

Other objects and advantages-of Vour invention will be apparent in thevfollowing description and and secondary pilot valves of Fig. 2, whichmechanism is illustrated schematically in Fig. 2;

Fig. 3 is a circuit diagram of the accumulator pressure control circuitillustrating the circuit` components in section;V

trative time delay valve and a four-way'valve to which the time delayvalve is connected; and

Fig. 5 is a sectional View through an illustrative by-pass valve thatmay be utilized in the circuit of Fig. 2. Y .Y i

General description A presently preferred commercial actuating unit isillustrated in Fig. 1, wherein a .pumping unit l0 is mounted on a frameII that mayroll on rails I2 when it is desired to withdraw the unit as awhole from the vicinity of an oil well having a ilow tubing I3projecting above the ground. The pumping unit IIJ includes a verticallydisposed hydraulic actuating cylinder .I4 with an actuating pistonor ramI4a axially slidable therein and a T-shaped sprocket head I5 mounted onthe top end of the ram. Over a pair of horizontally spaced sprockets I8is trained a chain I1, one end.of which is anchored at I9a to a dead-endrod I9 and the. other end of which is attached to a polish rod 21 bymeans lof aclevis I6. The actuating cylinder I4 is supported in anupright position by meansY of inclined braces 2l. Y.

The actuating ram I4a is operated byhydraulic iiuid under pressuresupplied by a pump 23,.and 45 Vv23, and the pressure fluid control valveoperating mechanism is actuated by a trip rod 26 secured to the sprockethead I5.

The clevis I6 on the chain I1 is coupled to a polish rod 21 acting asthe terminalsection. of a string of sucker rods passing downwardlythrough the flow tubing I3a to contact a reciprocating pump (notl shown)disposed below the oil level within the oil well. A stuing box 28secured to the top end of the tubing I3a seals` off the polish rod 21from the ilow tubing I3 to prevent leakage therefrom, and a suitableconnection (not shown) to the flow tubing I3 leads the pumped oil to asuitable reservoir or tank. Thus the entire hydraulic pumping unit I0causes a pumping action by means of the reciprocation of the sprockethead I5 by the actuating ram Illa which causes the chain I1 to raise andlower the polish rod 21 to thereby actuate the pump within the oil welland lift a column of oil in the flow tubing I3 to the earths surface. 4

The details of the hydraulic circuit of the pumping unit IU of Fig. 1are illustrated in Fig. 2. There it will be noted that the pump 23receives hydraulic fluid from a reservoir 29 and fio 4 delivers the uidunder pressure to an outlet pipe 3| connected to a relief valve 32, aby-pass valve 33, and a four-way valve 34. An exhaust or return conduit35 connects these three valves to the reservoir so that the samehydraulic fluid may be continuously circulated. The four-way valve 34 isactuated to connect two cylinder lines CI and C2 alternately to pressureand to exhaust, and accordingly reciprocates the actuating ram I4ainasmuch as these conduits are connected to opposite ends of thecylinder I4. The hydraulic ram unit comprises a stationary outer shell36having a concentrically mounted tube 31 projecting upwardly therein, tothe lower end of vwhich is attached the pressure line C2. A tubularVpiston 38 integrally formed on the lower end of the ram Illa makes asealing engagement Fig. 4 is an enlarged sectional viewhof'an'illusfwith the interior ofthe shell 36 and the exterior of the tubing 31 andreciprocates therebetween, the closed upper end of the ram I4a beingattached, to the sprocket head I5. Thus the eiective lifting area forpumped fluid is the outside diameter of the central tube 31, which areamay be designated as AI. The effective return stroke area of the piston38 is the annular space between the ram I4a and the outer shell 36, towhich the pressure supply line CI communicates, and which area isdesignated as A2. The area A2 is preferably and usually made smallerthan the area AI so as to effect a rapid return of the piston ascompared to the working stroke speed of travel, assuming a constantdelivery output from the pump 23.

The piston 38 isv normally urged upwardlyby means of pressure existentWithin the accumulator 22 acting Von the bottomof the, piston 38. Thusthe accumulator 22 may be provided with van outlet tube 39 coupled to aflow tube 4I that communicates with the interior of the cylinder shell36. The coupling of the flow tube 4I with the outlet tube 39 is enlargedto form a valve seat 42 for a surge poppet valve 43 normally urged to anopen position by means of a compression spring 44. Thus a normal flow ofhydraulic fluid from the accumulator to the ram will not cause operationof the poppet valve 43, but if the chain I1 should break or the stringof sucker rods should break, release of a load would cause` rapid riseof the piston 38 with a consequent rapid flow from the accumulator. Thisrapid flow would in turn cause the poppet valve 43 to seat, thusstopping flow from the accumulator through tubes 39 and 4I, and causingthe piston 38to move to its upper end position vat a slow rate of speedregulated by valve II8. Thus breakage due to the piston striking thepacking gland at the upper end of the shell 36 is avoided. In passing,it should be noted that thevaccumulator 22 is of the usual type whereina gas under pressure occupies the upper portion of the accumulator toact upon a hydraulic fluid disposed in the bottom part of theaccumulator tank.

As previously mentioned, our control circuit obtains a deceleration' atthe end of each stroke and a gradual acceleration at the beginning ofeach stroke by means of by-passing pressure fluid to exhaust, therebydiverting from the four-way valve its normal volumetric fluid supply andalso decreasing pressure-to the four-way valve. Thus the ram I4a, at theend of, each stroke, receives a vdecreasing supply of iiuidunderpressure, vthus causing it to slowdown to a stop;Y In this way themomentum of the loads being carried is lgradually decreased so asto,provide asmoothrevversal with, rod' stresses. k5 Whileit agregame i'woul'djbel possible to provide two projections on the -triprod26-adjacent each end so that the bypass' valve could1 be operated priorto the operation-of the four-way valve,- we prefer to initiate theYaction of both valves at the same time by a single projection at eachend.

Thus the trip rod 26 is provided with an upper projection 26a and alower projection 25h to act on a bell crank 45 illustrated in moredetail in Fig. 2a wherein it will be noted that one arm of thel bellcrank is bifurcated and the fork tips oiiset as at 45a and 45h.Accordingly the two projections or iingers 26d and 26o are disposed in.diiierent vertical planes so that the lower projection 26h will contactonly tipA 45a, and the upper projection 26a will contact only the othertip 451).V Thus the fingers 26a and 26h contact a tip and operate thebell crank to one extreme position or the other, at which position thetip will be disposed out of the path of travel of the particularactuating linger so that the linger passes the bell crank. Upon the nextreciprocation the linger that had just actuated the bell crank andtraveled past it would again travel past the bell crank withoutoperating it, but the other tip of the bell crank would be in the lineof travel of the other linger or projection. From the foregoing it willbe apparent that the neutral position illustrated in Fig. 2a is neverachieved as a rest position, `inasmuch as the bell crank 45 should be inone extreme position or the other. This attainment of an extremeposition that will rotate the tip just actuated out of the path oftravel of the acuating linger may be assisted by an over-centercompression spring 461 contacting a portion of the bell crank 45.

We also prefer to operate the by-pass valve 33 and four-way valve 34 bymeans of pilot valves rather than by direct mechanical actuation. The

bell crank 45, for this purpose, is connected by a link 46 to thecontrol handles of a primary pilot valve 41 and a secondary pilot valve48. Both the pilot valves 41 and 48 are simple four-way valves, and areillustrated as being of the rotary type. The primary valve 41 isconnected to pressure and to exhaust by means of conduits 49 and 5I,respectively, thus giving a unidirectional supply to the primary pilotvalve. The secondary pilot valve 48 is, by contrast, connected byconduits 52 and 53 to the cylinder lines Cl and C2 so as to obtainalternating pressure and exhaust c onnections. The cylinder lines of thesecondary pilot 48 are connected through metering valves 54 to oppositeends of the pressure-driven by-pass valve 33. The cylinder lines 56a and51a of the primary pilot valve 41 are connected, however, to oppositeends of a time delay or relay valve 55 which, after a time period of anappreciable duration, supplies pressure andexhaust to opposite ends ofthe four-way valve 34 through lines 56h and 51h.

From the foregoing description itwillbe apparent that a single linger26a or 26h on the trip rod 26 may initiate the actuation of the by-passvalve 33 and the four-way valve 34 at the same time, but because of theinterposition of the time delay valve 55, the actuation of the four-wayvalve 34 will be delayed until immediately following the traverse of theby-pass valve 33. Furthermore, as will be apparent from an inspection ofFig. 5, the by-pass valve 33 has a time-graduated capacity so that atthe end of the delay period of the time delay valve 55, the by-passvalve 33 will b'e passing substantiallyall of the output ofk thepump23'. The timev delayvalv'e' 55 is' controlled by adjustmentsindicated-11ml Eig.: 4 to-co'ntrolits rate of speed, and themeter valves54 in the circuit of by-pass valve' 33 areL also manually adjusted -sothat the -time of full. ii'ow of thev vby-'pass valve 33 will coincidewith. the period ofthe time delay valve 55. Also the posi'.- tionof tripfingers 26a and. 26h on trip rod. 26 may' be adjusted in conjunctionwith the valves togive-an acceleration and deceleration travel of anydesired length.

The control of the pressure in the accumulator 22 is also illustrateddiagrammaticallyin. Fig.. 2.. Thus if there is a deii'cient pressurewithinl the accumula-tor 22,.a make-up pump 58fis automaticallyEoperatedl to pump air into a line 259. con.- nected to the accumulator22.- ()n theother hand, if thegas pressure of the accumulator isexcessive, ablowdown valve 6| is operated automatically to release airor other gas from.y the accumulator 22 through a conduit 62. The maincontrol element of the accumulator pressure circuit is a stroke controlvalve 63 which is urged upward by hydraulic iiuid under pressuresupplied by a conduit 64 and which is mechanically driven downwardly bythe sprocket head l5 acting through a vertically disposed drive rod 65,the top end of which is positioned so as to be engaged by the head I5 asit nears the lower extremity of the-stroke.

I Detail description of power clutch The detail construction of thepower circuit may be explained withl reference to Figs. 4 :and 5*, Vaswell as to Fig. 2. Referring to Fig. 4, it will 'be noted that the timedelay valve 55 includes a barrel 66 having an exhaust port 61 and twocylinder ports 68 and 69. The exhaust line 5|. is connected -to the port61, and the cylinder lines 51h and 56h are connected to the ports 68 and69, respectively. The opposite ends of the barrel 66 are closed withidentical-caps 1|, including pipe iittings 12 communicated by means ofcheck valves 13 to the interior of the barrel 66. The check valves :areby-passed by adjustable needle or metering valves 14a and 14h. Adouble-landed spo-o1 15 is slidably disposed within the barrel 66 toreciprocate between the two end `caps 1|. When pressure fluid fromprimary pilot valve 41 is applied at one end of the time delay valve 55,for example the left end, it flows through the check valve 13 to theinterior of the barrel 66,

forcing the spool 15 to the right, and the Huidtrapped at the right endof the valve isforced outwardly through the meter valve 14a. When thespool has moved to the right suihciently to uncover port 68, there willbe a direct communication between the left hand line 51a and itsassociated line 51h, `and the pressure fluid wil-l pass through line 51hto shift four-way valve 34. The length of time delay between theapplication of pressure fluid to the left hand end of the time delayvalve 55 and the shifting of the fourway valve 34 is governed by therate of metering of exhaust uid through the meter valve 14d'. As thespool 15 moves to the right, the line 56h will be communicated to theexhaust line 5i. When the pressure from the primary pilot valve 41 isreversed, the valve moves to the position illustrated in full outline inFig. 4, communicating the line 511) to exhaust and interconnecting lines56a and 56h. The time delay as the valve spool moves to the left isgoverned by the rate of metering of exhaust fluid through the metervalve 14h. A

' An illustrative four-way valve 34 for operation with the system isalso indicated in Fig'. 4.- This `valver includes a main housing16havingya cenjf tral bore 11 in which is disposed a Adouble-landed spool18, which spool is provided with projecting ends 19a that act aspistons. The housing .16 has two cylinder ports formed therein to whichthe lines CI and C2 are connected, and alsorhas acentral pressure port19 disposed betweenthe two cylinder ports. Exhaust i'luid is dischargedthrough a bifurcated exhaust passage 8| to which the exhaust pipe 3'5 isconnected. The housing 16 also has cylinder chambers 82 formed at eitherend thereof communicating With the actuating lines 56b and 51h. In theposition illustrated, cylinder line C2 is connected to pressure port 19,whereas vcylinder line CI is connected to exhaust conduit 35. If thepressure and exhaust in actuating conduits 56h and 51h are reversed, thespool 18 will slide toward the right to reverse this condition of flow.Y

An illustrative construction for the yby-pass valve 33 is shown in Fig.5, wherein it will be noted that a housing 83 has'ports 84 at each endlto communicate with the lines from the secondary pilot valve 48. Thehousing 83 also is provided centrally with axially spaced ports 85 and86 communicated to the pressure pipe 3| and to the exhaust pipe 35,respectively. A doubleheaded piston 81 is disposed within the'housing 83to move in response to the direction of application of pressure andexhaust atthe ports 84, and has one head slotted with tapering grooves88 to provide a condition of graduated flow from pipes 3| to 35 as thepiston 81 moves in the bore. The rate of speed of movement of the piston81 may be carefully regulated by the meter valves 54 (Fig. 2). Anadjustable threaded stop 89 is provided to establish the maximum flowconditions through the valve when the piston 81 is at the full flowposition illustrated. As previously mentioned, the secondary pilot valvewhich operates the by-pass valve 33 has its inlet and exhaust pressuresreversed by reversal of the four-way valve 34 due to the connection tolines CI and C2. Forthis reason the spool 81 will be returned to anonflow or non-by-pass condition shortly after the four-way valve hasbeen operated.

Detail description of accumulator pressure control circuit The detailconstruction of the accumulator pressure control circuit is illustratedin Fig. 3, wherein the parts previously identified in connection withFig. 2 are illustrated, including the main control element, the strokecontrol valve 63, as well as the make-up pump 58 and the blowdown valve6|. The stroke control valve 63 includes a valve housing 9|, a dashpothousing 92, and an actuating cylinder housing 93 Vairranged end-to-endin axial alignment. A central stem 94 passes through all three housingsand has a reduced portion 95 at the valve housing 9|, a check valvepiston 96 disposed in the dashpot housing 92, and a piston head 91 disposed within the actuating cylinder 93. Pressure is supplied to thevalve 63 by means of the con. duit 64, previously identified,communicating with the fluid pressure pipe 3|, which pressure fluidpasses through a check valve 99 to the actuating cylinder 93 to forcethe stern 94 upwardly. A branch conduit 98 supplies pressure fluid to aport in the valve housing 9|. A second port in the housing 9| isconnected to a conduit |02, and a third port |03 is connected to aconduit |04 lleading to the reservoir 29.V

The dashpot 92 of the valve 63 is the central control element of thevalve 63 and is provided with an external metering circuit including aconduit |05 and a metering valve |06. The dashpot piston 96 is aperturedto permit passage of liquid therethrough on the down-stroke, but has acheck valve |01 which closes the aperture on the up-stroke to give riseto the dashpot action. The normal lower position of the stem 94 with thedashpot piston 96 is illustrated in Fig. 3, and it will be noted that itis spaced an appreciable amount from the bottom of the containingcylinders. It will also be noted that in this position, the pressureport |0| remains covered by the stem 94.

As stated previously, deficiency of gas pressure in the accumulator willtend to permit the ram to over-travel its normal point of reversal.Accordingly, the sprocket head |5 in contacting the drive rod 65 willdrive it and the stem 94 below its normal position due to the fact thatthe entire hydraulic cylinder is permitted to drop below itspredetermined lower point. The driving of the piston 96 below its normallower point will cause communication between the pressure port |0| andthe conduit |92, causing pressure iiuid to iiow through that conduit toa three-way valve |09, causing a spool in that valve to be raised, asillustrated, against the compression of a spring ||2. In the illustratedposition, pressure uid from cylinder line C2 will be Vcom--I municatedby a conduit ||3 through the valve |09 to a conduit I4 connected to thebottom end of the hydraulically actuated make-up pump 58. Inasmuch aspressure will exist in the cylinder line C2 on the up-stroke of theactuating ram |4a, this pressure will cause a piston ||5 within the pump58 to rise, thus compressing air and forcing it outwardly through theconduit 59 to the accumulator 22. At the time that cylinder line C2 isunder pressure cylinder line Ci will be subject to exhaust, andaccordingly a conduit ||6 connected to the exhaust will permit thepiston ||5 to move freely upwardly. Upon the downstroke of the actuatingram Ma, iiuid under pressure will pass through the line l |6 to act onthe pump piston ||5, forcing it downwardly because the three-way valve|09 will then be in its rest position because the rise of the stem 94will close off the pressure port |0| and open exhaust port |03. Thespool I|| of the three-way valve will then communicate the conduit ||4to the reservoir. The over-travel of the ram |4a will continue, and themake-up pump will deliver a charge of air to the accumulator on eachstroke until accumulator pressure has been returned to normal.

When the accumulator gas pressure is excessive, the hydraulic ram willtend to under-travel its normal bottom reversal point, and consequentlythe stern 94 will not be returned to the normalv position illustrated.,The .normal rise of the piston 96 on its dashpot action will cause theupper end of the stem 94 to Contact a valveoperating lever to actuatethe blowdown valve 9| and thereby relieve gas pressure from theaccumulator. The under-travel and resulting blowdown will continue oneach stroke until accumulator pressure has been reduced to normal.

Operation The operation of the power control'for our pumping unit maybest be described with refer# eneiio Fif-1 e119? -.The primemver. 2,4..ma:

mst mbe energized, causing .the pump 12.3 t0 :be actuated, drawing.fluid vfrom reservoir 29 :and .delverins-ittogpipel. The pump may beofany suitable type that develops a requisitepressure, .but -we. preferto use a constantfspeed constantdisplacement jtype vof pump, protectedagainst voverload/by. relief val-ve )32.

`The operation of the ram 14ar is continuous and @automatic and isprincipally effected by the four-way valve 34 which is connected between,the pressure line -3I and the exhaust linev35. Accordingly pressure andexhaust alternately .exist in the cylinder lines CI and C2 connected,respectively, to the 'top andthe bottom of the hydraulic cylinder |14.Pressure -in line C2 is .delivered tothe central-tube 31 of -theram andacts over'the-area AI to liftthe ram. Fluid under pressure in theaccumulator 22 passes through conduits 39 and 4I to act on the bottomofthe piston 38. The entire sprocket'head -I5 is consequently lifted,causing a twofold movement of T thechain l1 connected by the clevis ltothe `polish rod 21 .of the oil Well.

When the actuating ram '14a approaches the end o f its stroke,theiinger'Z'Bb on `the trip rod .26 connected to the sprocket head I5engages the -bell v'crank 145, shifting the link 46 andconsequentlyshifting rthe pilot valves 41 and 48. The pilot valve 41 iacts toreverse the four-way .valve 34, .but this .actuation is delayed Abecauseof the. interposition of the *time delay valve 55 in .thecircuiu as isbest'illustrated in Fig. 4. The actuation of the by-pass valve 33 isstarted immediately by delivery of fluid under pressure to therightehand end (Fig. 5) ofthe by-pass valve 33, causing its piston 81 toshift to the left to the position villustrated in Fig. 5. This .shiftvis not immediate, however, but vis slow `in `acting due to the controlof vthe rate of exhaust as determined by the `setting of the meter-valve54.

The flow vof iluid to actuate the by-pass valve 33 to decelerate the ramas its approaches the end'of Vits downstroke can b e traced from thecylinder line CI, via pipe 52, secondary pilot valve 4 8, ,meter valve5.4 at theright, and port 84 Aat the right into the right end ofcylinder `3.3. .The left'end of this cylinder isrelievedvia port 84 attheleft, meter valve 54 at the left, secondary pilot .valve .48,.andpipe 53 to cylinder line C2. The vi low. to actuate this valvetodecelerate v the fram as it approaches the end of its upstroke issimilar, exceptthatthe actuating uid comes'from cylinder line C2 andpipe 53 andthe valve gis relieved to pipe 52 and cylinder line CI.

The effect of the opening of the by-pass valve 33 is to divert from thefour-way valve 34 a part of the normal output of the pump 23. As thehydraulic cylinder approaches its upper stop, an increased amount isby-passed due to the movement of the piston 81 to the left until finallyonly a small flow of iiuid is left for the four-way valve '34. Theeffect-is a'gradual slowing of the piston 38 of the -ram Ma, causing aslowing of the associated string of sucker rods and the column of oilbeing lifted tothe surface. Thus, reversal o f :the rods isvaccomplished gradually at the ends ofthe stroke,with minimum reversalstresses induced therein. As the ram piston `38 reaches the end of itsupward travel, the time delay valve 55 will'permit the control fluidfrom the pilot valve 48 to shift the four-way valve 34, and accordinglythis shifting of the valve will take place under a reduced pressure anda refi10 Y d1-iced. .fluid,flow rvcondition, .thus relieving the .valveor" major loadsduring movement.

The `flow of fluidftoactuate the yby-pass .valve ,33 to acceleratetjlieram as itstar-ts its upstroke can b e-traced from .the cylinderline C`2,-via pipe :53, secondary lpilotvalve 48, meter valve 54 at .the left, and port 84 at the left .into vthe left end of ycylinder 83. Theright end of Athis cylinder is relieved via port 84 at the right, metervalve -54 at the rig-ht, secondary pilot valve 48, and pipe 5 2, tocylinder line CI. The -flow to actuate this valve to accelerate the ramas it starts its downstroke is similar, except that the actuating fluidcomes vfrom cylinder line CI and pipe 52 and A'the ,valve is relieved topipe 53 and cylinder AlirleC'L While we have shown and described thepreferred embodiment of our invention, we do not desire to be limited toany of the details shown and described, except as defined by the termsofthe followingclaims We claim:

y1. A hydraulic pumping unit comprising: a reservoir; apower driven pumpreceiving fluid from the reservoir; a four-way valve having a pressure.port connected'to the pump output and having an ,exhaust port connectedto the reservoir; a cylinder containing an actuating ram and beingconnected to the four-way valve for reciprocation of the ram, a by-passvalve connected between the pump output and the reservoir in parallelwith said four-way valve; an automatic .actuatorfor voperating theby-pass valve as the ram approaches the end of each stroke in eitherdirection,zwherebythe fluid delivered to the four- Way vrvalve isgradually reduced to decelerate the hydraulic ram prior to reversal andgradually increased to accelerate the ram after reversal; and lanautomatic actuator for operating the four-wayvalve at the end ofeachstroke to cause the reversal of `theram.

12. A :hydraulic pumping unit comprising: a reservoir; va power drivenpump receiving ifluid from 7the reservoir; a foureway valve connected tothe pump output and to the reservoir; a, cylinder containing anactuating ramand'being hydraulically connected to the four-way valve forrecipro'cation of the ram; a by-pass valve connected between the pumpoutput and the reservoir in parallel with said four-way valve; a singlemechanical actuator mechanically coupled to the ram formovementinresponse to ram actuation andadapted to initiate operation of theby-pass valve and the four-way valve near the end of each stroke of theram in either direction; and atime delay mechanism for the four-wayvalve, whereby the by-pass valve will be first operated to `decelerate,the hydraulic ram and thereafter the fourway valve will operate toreverse the hydraulic ram, after which the by-pass Valve will operate toaccelerate the ram inthe vopposite direction.

3. A ,hydraulic .pumping unit comprising: a reservoir; apump adapted toreceive fluid from the reservoir; a four-way valveconnected to the pumpoutput and to the reservoir; a hydraulic actuating cylinder; a pistonand.ram slidable .in said, cylinder ,a pair of vcylinder lines connectingthe actuating cylinder to thefour-,way valve ,so that alternateconnection of the lines to pressure and exhaust will cause areciprocating motion of a piston and ram in the actuating cylinder; ahydraulically operated by-pass valve disposed between the pump outputand the reservoir in parallel with said four-way valve and normally 11maintained in a closed position; a pilot valve for operating the by-passvalve by means of pressure fluid from ,theVV cylinder lines; and anactuator for the pilot valve to operate it a predeterminedvdistance fromthe end of the stroke in either direction, whereupon the by-pass valvewill gradually reduce the fluid supply to the fourway valve prior toreversal of the four-way valve to thereby decelerate the actuating ram,and, after reversal of flow in the cylinder lines by actuation of thefour-way valve, will gradually increase the fluid supply to the four-wayvalve to thereby accelerate theactuating ram. g 4. A hydraulic pumpingunit as defined in claim 3, including a meter valve interposed betweenthe pilot valve and the by-pass valve to regulate the speed of operationof the by-pass valve,

5. In a hydraulic pumping unit: a source of hydraulic fluid underpressure; an actuating cylinder; a ram in said cylinder; a four-wayvalve connected to the source and to the cylinder for selectivereciprocation of the ram in the cylinder; a by-pass valve connected tothe source in parallel with said four-way valve to control the fluidsupply available to the four-way valve; a pilot valve connected to theby-pass valve for operating the by-pass valve; a ltime delay relay valvecoupled to the four-way valve; another pilot valve coupled to the timedelay valve; and a single actuator for simultaneously actuating bothpilot valves a predetermined distance prior to the end of the stroke ofthe ram in either direction, whereby the by-pass pilot valve will actimmediately to commence opening the by-pass valve, but the opening ofthe four-way valve will be delayed due to the action of the time delayvalve.

6. A hydraulic pumping unit comprising: a fluid reservoir; a powerdriven pump adapted to receive fluid from the reservoir; a hydraulicallyoperated four-way valve connected to the pump output and to thereservoir; a two-way actuating cylinder and ram; cylinder linesconnecting opposite ends of the cylinder to the four-way valve forselective reciprocation of the ram; Va hydraulically operatedby-pass'valve connected between the pump output and the reservoir; aprimary four-way pilot valve having pressure and exhaust connections tothe pump cutput and the reservoir; a time delay valve coupled to theprimary pilot valve and coupled to the four-way valve for actuation ofthe four-way valve and having adjustments for regulating delay time; asecondary four-Way pilot valve having pressure and exhaust connectionsto the cylinder lines and connections to the by-pass valve, each ofwhich includes a meter valve, for operation'of the by-pass valve; and asingle actuator for simultaneously operating both pilot valves prior tothe end of the stroke of the actuating ram, whereby the by-pass valvewill be gradually opened, at a rate dependent upon the setting Vof theVmeter valve, to effect a deceleration ofthe actuating ram, after whichthefour-way valve will be operated to effect reversal of the actuatingram, following which the four-way valve will supply fluid in oppositesense to the secondary pilot valve to elect gradual closure of theby-pass valve at a rate dependent upon the 12 setting of the other meterAvalveto produce acceleration upon beginning of the next stroke.

7. In a hydraulic pumping unit employing an accumulator and a hydraulicactuating cylinder ram having a possible stroke in excess of a pump tobe actuated, a control circuit for the gas pressure of the accumulatorso as to eiect a constant predetermined stroke of the actuating ramcomprising: a stroke-control valve whose spool is normally urged in onedirection; a drive rod contacted by the actuating ram to return thespool toward a normal position upon each complete cycle of the actuatingram; a power operated make-up pump adapted to deliver gas under pressureto the accumulator; a control circuit for the pump adapted to beoperated by movement of the spool past a normal lower position; and ablowdown valve for the accumulator adapted to be operated by the spoolwhen it moves beyond its normal upper position.

8. A hydraulic pumping unit comprising: a reservoir; a constant-volume,power driven pump adapted to receive liquid from the reservoir; afour-way valve; a two-way cylinder connected to the four-way valve andhaving an actuating ram mounted therein for selective reciprocation; anactuator for the four-way valve operative to reverse the valve at theends of the stroke of the actuating ram; an accumulator for assistingthe pump on the pumping stroke; a stroke-control valve whose spool isurged in one direction by pressure from the pump; a drive rod contactedby the actuating ram to drive the spool lin the opposite direction atthe end of each cycle of the actuating ram; a make-up pump coupled tothe accumulator to deliver gas under pressure thereto; a blowdown valveconnected to the accumulator to relieve gas pressure therein; a valveactuated by the stroke-control valve and responsive to the valve spoolwhen driven past its normal position for actuating the pump; and anactuator coupled to the spool for actuating the blowdown valveresponsive to the spool rising above its normal limit in response topressure fluid.

9. A hydraulic pumping unit as defined in claim 8 wherein the make-uppump is hydraulically actuated and is connected to cylinder linesextending from the four-way valve to the cylinder, and wherein thestroke-control valve controls a three-way valve in one ofthe connectionsto the cylinder lines so as to selectively operate the make-up pump.

PAUL E. NOLL. T. DWIGHT ALLER.

REFERENCES CITED n The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,619,475 Hubbard Mar. 1, 19271,910,766 Hobson May 23, 1933 1,978,346 Ernst et al. Oct. 23, 19342,044,777 Erling June 23, 1936 2,051,052 Morgan Aug. 18, 1936 2,160,217Kingsbury May 30, 1939 2,192,778 Stacy Mar. 5, 1940 2,347,302 Twyman etal. Apr. 25, 1944 Certificate of Correction Patent No. 2,57 2,748October 23, 1951 PAUL E. NOLL ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Column 6, line 30, for clutch read circuit;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the Patent Oiice.

Signed and sealed this 19th day of February, A. D. 1952.

THOMAS F. MURPHY,

Assistant Gommian'oner of Patents.

